Drum-type washing machines are widely used especially in Europe. Commercially available drum-type washing machines typically perform a laundering process, including a washing process and a rinsing process, in both of which a rotary drum is rotated at low speed, and a spin-drying process, in which the rotary drum is rotated at high speed, often followed by a air-drying process.
FIGS. 13 and 14 show a conventional drum-type washing machine. FIG. 13 is a vertical cross-sectional view of the conventional drum-type washing machine as seen from a side, and FIG. 14 is a vertical cross-sectional view of the conventional drum-type washing machine as seen from the same side but at a different cross-section. A cabinet 201 has, open in a front face thereof, a laundry opening 201a that can be opened and closed with a door 202. Inside the cabinet 201, a cylindrical water tub 203 is provided that has a water tub opening 203a open toward the laundry opening 201a. With respect to a horizontal axis, the cylinder axis of the water tub 203 is so inclined as to be increasingly low rearward. The laundry opening 201a and the water tub opening 203a are connected together by a tubular connecting member 204 that forms a watertight passage between them. The connecting member 204 has part thereof formed into a bellows portion 204a that makes the vibrations of the water tub 203 less likely to conduct to the cabinet 201.
Inside the water tub 203, a cylindrical drum 205 is provided that has a drum opening 205a open toward the water tub opening 203a. With respect to a horizontal axis, the cylinder axis of the drum 205 is so inclined as to be increasingly low rearward. All over the cylindrical circumferential surface of the drum 205, a large number of small holes 205b are formed. Through the small holes 205b, air and liquid pass between inside the water tub 203 and inside the drum 205. On the inner wall surface of the drum 205, baffles 205c are provided that protrude toward the cylinder center axis of the drum 205.
From the center of the rear surface of the drum 205, a drum shaft 205d protrudes rearward. The drum shaft 205d is fitted so as to penetrate the rear surface of the water tub 203, and is, via a bearing 207, rotatably supported on a bearing housing 206. The drum 205 is coupled, via the drum shaft 205d, directly to a motor 208 fitted on the rear surface of the water tub 203. As the motor 208 is driven, the drum 205 is driven to rotate.
In a front part of the drum 205, a balancer 209 is provided that has a movable material sealed therein. The balancer 209 reduces the swings of the drum 205 when it is driven, and thus contributes to reduced generation of vibrations. The balancer 209 itself is a weighty member, and thus contributes to an enhanced rotation balance.
At a bottom part of the water tub 203, as shown in FIG. 14, a water drain duct 210, a water drain valve 211, and a water drain hose 212 are provided. When the water drain valve 211 is opened, water inside the water tub 203 is drained out of the cabinet 201 via the water drain duct 210 and the water drain hose 212.
Over a rear to upper and to front part of the water tub 203, a warm air feeding device 213 is provided. The warm air feeding device 213 includes a warm air return port 214, a heat exchanger 215, a coupling duct 216, a fan device 217, a duct 218, a heating device 219, and a duct 220. One end of the duct 220 is connected to a warm air discharge port 204b formed in the connecting member 204, so as to lead into the water tub 203. During an air-drying operation, the warm air feeding device 213 sucks in the air inside the water tub 203 via the warm air return port 214, and circulates it through the heat exchanger 215, the coupling duct 216, the fan device 217, the duct 218, the heating device 219, and the duct 220 to return it, via the warm air discharge port 204b, into the water tub 203. In this way, the air inside the water tub 203 is warmed and is subjected to heat exchange (dehumidification).
Moreover, as shown in FIG. 13, at a front upper part of the water tub 203, a counterweight 221 is fitted, and, at a front lower part of the water tub 203, another counterweight 222 is fitted. These counterweights 221 and 222 are for adjusting the center of gravity of a structural load 223, which will be described later. By varying the weights of the counterweights 221 and 222 and the fitting positions thereof on the water tub 203, it is possible to easily vary the center of gravity and the weight of the structural load 223, leading to higher freedom in design.
The water tub 203 is supported inside the cabinet 201 by suspensions 224, restricting springs 225 and 227, and a coupling member 226. The suspensions 224, of which one is provided at the left side and the other at the right side, supports the water tub 203 from below. The restricting spring 225, which is a tension coil spring, applies a front/rear-direction tensile force between a front upper part of the water tub 203 and a front upper part of the cabinet 201. The restricting spring 227, which also is a tension coil spring, applies a front/rear-direction tensile force between the coupling member 226, which is fixed to a middle upper part of the cabinet 201, and a front upper part of the water tub 203.
Here, the suspensions 224 and the restricting springs 225 and 227 bear the structural load 223 of, and thereby support, the following components: the water tub 203, the drum 205, the drum shaft 205d, the bearing housing 206, the bearing 207, the motor 208, the balancer 209, the heat exchanger 215, the duct 216, the fan device 217, the duct 218, the heating device 219, the duct 220, and the counterweights 221 and 222. The two, left and right, suspensions 224 support the water tub 203 at one position in the front/rear direction, and are located substantially at the center of gravity g of the structural load 223 in the front/rear direction.
Different processes included in a laundering process, namely a washing process, a rinsing process, and a spin-drying process, and also an air-drying process, are all performed by driving with the motor 208 the drum 205 to rotate, with the drum 205 in a state containing a laundering load 228, which includes laundry put into the drum 205 as articles to be processed plus washing water to be used to process the laundry. In a washing process, the motor 208 is driven to rotate intermittently, alternately in the forward and reverse directions, at comparatively low rotation speed so that the drum 205 rotates intermittently, alternately in the forward and reverse directions. In the spin-drying process, the motor 208 is driven to rotate continuously in one direction at high rotation speed so that the drum 205 rotates at high speed.
In the drum-type washing machine constructed as described above, when the drum 205 is driven to rotate in a washing process, the suspensions 224 are located substantially at the center of gravity g of the structural load 223, resulting in a good rotation balance. Moreover, the provision of the restricting springs 225 and 227, which elastically restrict the front/rear-direction swings of the structural load 223, helps reduce the front/rear-direction swings of the structural load 223, effectively reducing the vibrations generated in the cabinet 201.                [Patent Publication 1] JP-A-2000-262796        